Activated carbon and pH Jump??

[arking_mark]

So I decided that my tank was looking a little too cloudy and wanted to run some activated carbon to clarify the tank.

Within about 30 minutes of starting carbon filtering through a reactor, my pH jumped from 8.30 to 8.37. The setup was a pump from my sump chamber through the reactor to the return chamber and bypassing my skimmer.

As my skimmer is used to control my pH it came on using house air (high CO2) to drive down the pH. Within about 10-15 minutes of turning off the reactor, the pH went right back down to 8.30 which is my setpoint.

I'm trying to sus out why the pH jumped from running an activated carbon reactor.

The sump volume is roughly 20gal and the total volume of my system is about 105gal.

The reactor was probably moving about 120gal/hr.

Normally, I expect increased water movement to reduce my pH as my air has higher CO2.

I'll experiment a little with this and see what I can deduce.

Any insights would be appreciated...does activated carbon do anything to raise pH?

 

[arking_mark]

Ok. Not sure what happened. Just turned the filter back on and the pH is stable as expected...weird.

 

[Righteous]

Maybe line interference from the new reactor pump?

 

[shneerf]

My guess is with any reactor off you have a whole "batch" of fluid concentrated (or this case highly filtered) fluid was sitting in the reactor now suddenly dumping its entire volume into the tank. Not sure why AC would do that, I never fully understood what AC removes exactly but my guess is that it's removing some acids.

 

[Randy Holmes-Farley Verified Community Expert]

If there was water stored in the reactor, the biological degradation of organics will produce CO2 and lower pH.

GAC itself usually has a quite small effect on pH, but if you do not rinse it, it may have some.

 

[arking_mark]

If there was water stored in the reactor, the biological degradation of organics will produce CO2 and lower pH.

GAC itself usually has a quite small effect on pH, but if you do not rinse it, it may have some.

There was no water stored in the reactor...

I think I must have disturbed the pH meter or something. I could not repeat the changes...and there is nothing I could imagine that would very quickly raise and lower the pH with GAC.

 

[Randy Holmes-Farley Verified Community Expert]

There was no water stored in the reactor...

I think I must have disturbed the pH meter or something. I could not repeat the changes...and there is nothing I could imagine that would very quickly raise and lower the pH with GAC.

Thanks for the update! :)

 

[DrZoidburg]

This ph rise here could be from how they activate the carbon. You could be looking at trace sodium hydroxide contamination, or calcium.

 

[Fuzzball]

This raise in ph happens to me every time I replace the carbon..?

 

[Fuzzball]

This raise in ph happens to me every time I replace the carbon..?

 

[Randy Holmes-Farley Verified Community Expert]

What exactly do you observe when adding what exactly?

 

[BluesClues]

What exactly do you observe when adding what exactly?

Hey Randy hoping to re visit this subject I’m having the same PH jumb when I replace my Catalytic Activated Carbon. I use 300grams in a BRS Small reactor and I replace it once a week when I notice my PH start to slump. I’m doing Kalkwasser Via a Reef Octo KS-150 reactor dosed to my PH set point of 8.5. I thought it was because yellow pigments blocking light but my PH is lower at night also thoughts?



In this graph I just replace my carbon and got a sudden jump in PH and you can see the more aggressive spikes at night leading up to the change. The massive drop down is a %25 water change on 120 gallons.

 

[Randy Holmes-Farley Verified Community Expert]

GAC binds organics that might otherwise degrade, producing CO2 and lowering pH.

If the new GAC placed in a small amount of tank water does not cause a substantial and immediate pH change , then I expect the above explanation is the reason.